Many vehicles include a cruise control system that allows a driver to control vehicle speed during operation of the cruise control system without depressing an accelerator pedal. A controller maintains the vehicle speed through varying road and vehicle conditions. The driver can manipulate the cruise control using on/off, set/coast and resume/accelerate switches as well as using a brake pedal and/or a clutch pedal.
Originally, cruise control systems were developed for vehicles using mechanical throttle control (MTC). MTC regulates throttle movement via a mechanical cable that opens and/or closes the throttle. The movement of the throttle is proportional to driver input through the accelerator pedal. When the cruise control system is activated, a stepper motor drives the mechanical cable linkage to the throttle. The stepper motor includes an electronic control unit (ECU) that does not receive data from a controller. In effect, the MTC only receives input from a transmission vehicle speed sensor. The speed sensor, however, is susceptible to excessive noise. As a result, cruise control systems use a speed error approach, which compares vehicle speed to a desired speed.
Advancements in vehicle technology include less noisy vehicle speed sensors and electronic throttle control (ETC), which replaced MTC. The advent of ETC enables modification of the cruise control system based on controller parameters that were previously inaccessible using the stepper motor architecture. However, instead of developing modern cruise control algorithms, pre-existing cruise control algorithms have been adapted to meet the changing performance requirements.